The present invention relates to a new and improved heat-dissipating socket connector for leaded modules. More particularly, it relates to a socket connector including a module-receiving recess which is angled up and off the surface of a printed circuit board and disposed at a heat dissipating angle, to provide a reliable electrical connector having reduced board space requirements.
Leaded modules, and small outline J-leaded devices (SOJs) are known. These J-leaded integrated circuit packages have traditionally been mounted flat on a printed circuit board and soldered at the curved end of the J lead to conductive pads on the printed circuit board. These SOJ devices have been used, for example, to increase memory of an electronic device and for other purposes. Although J-leaded devices of this type are intended for prolonged use, problems do arise from time to time with directly mounted and soldered-on devices.
In use, these devices can generate very high ambient temperatures, particularly at their metallic lead portions. These high ambient temperatures can lead to solder joint failure of some or all of the J-leads, which are difficult to visually inspect with a flat mounted SOJ package device. In addition, the development of very high ambient temperatures in use may be associated with a reduction in the electrical reliability of the leaded module itself. Moreover, the development of high temperatures in use may also adversely affect the electrical performance of other electrical components mounted in the same housing of an electronic device.
Some of these disadvantages have lead to the development of leaded module socket connectors which generally include a dielectric frame or housing including a plurality of metallic terminals which are adapted to engage the module leads. Illustrative examples of prior art socket connectors for leaded modules include U.S. Pat. No. 4,511,201; U.S. Pat. No. 4,558,397; WO No. 84/01859; and U.S. Pat. No. 4,645,279.
Each of the above-mentioned patents describe socket connectors including a dielectric frame member mounted in a coplanar manner with the surface of a printed circuit board. Terminals are disposed within the frame in order to make high pressure contact with the leads of an integrated circuit device. These board mounted sockets are intended to provide a mounting arrangement for a leaded module which is relatively more permanent than the module itself in use.
One major shortcoming associated with each of these coplanar socket arrangements is that the connector frame requires a larger amount of board surface area than would be required for mounting a J-leaded device directly to circuit elements on the base printed circuit board. Secondly, the coplanar mounting arrangement does not provide for heat dissipation to relieve the thermal stresses brought on by the high temperatures generated by the leaded devices in use. These prior arrangements permit very high ambient temperatures to be developed at the under side of the leaded device, between the upper surface of the printed circuit board and the device. The high temperatures in turn generate thermal stresses within the dielectric frame material which can result in warpage of the frame and misalignment for the terminals mounted in the frame.
Another major shortcoming provided by the above-mentioned coplanar socket connectors is that the solder connections between the socket terminals and the base printed circuit board are generally obscured by this arrangement. In the event of a failure of one or several of the solder joints or terminals, the entire device must be removed to identify the cause of electrical failure or intermittency. The result is that repair and and maintenance are extremely costly and this is a very serious shortcoming of prior art leaded module socket devices.